Anatomy. - The nucleus of BELLONCI in birds. By J. L. AOOENS. (From the Dutch Central Institute for Brain Research, Amsterdam.) (Communieated by Prof. C. U. ARIËNS KAPPERS.)

(Communicated at the meeting of September 28, 1940.)

In a paper published in these Proceedings (Vol. 41, 1938) I described in the rabbit and aardvark a nucleus, Iying in the common stem of the lateral components of the stria medullaris, which I homologized with the nucleus ovalis of reptiles. Before me, in mammais, the same nucleus had been noticed by Miss GII.BERT (1935) 1) in the hu man embryo, who already interpreted it as a nucleus ovalis, and by YOUNG (1936) in the guinea pig, who, however, regarded it as but an encapsulated portion of the interstitial nucleus of the stria terminalis.

The nucleus ovalis is a small ellipsoidal cell group in the foremost part of the thalamus, first described by HUBER and CROSBY (1926) in the Ameriean alligator 2) and subsequently also demonstrated for the other reptilian orders, with the exception, hitherto, of snakes. Most recently it was reported by STRÖEI< (1939) for Lacerta vivipara. Looking for homologues, in the Anamnia, of this cell group, I came to the conclusion in the paper cited at thc outset that it corresponded with a nucleus described by BELLONCI (1888) in the frog as the "vorderer oberer Nucleus des Corpus genieulaturn thalamicum", a homology, already suggested by CAIRNEY (1926) and PAPEZ (1935). HERRICf( (1925), who studied this nucleus in great detail in amphibians, and found that it is a correlation centre for oifactory, optie and somesthetic impulses, called it nucleus of BELLONCI. This term I also applied to the homo\ogous nuclei of repti\es and mammais, since HERRICf('s term (1925) had the priority over HUBER and CROSBY'S (1926). Moreover, the term ovalis may give rise to con fusion with similar ones, used for other thalamic nuclei, viz., ovoida\is and ovoideus.

The nucleus of BELLONCI, first noticed in amphibians, thus ha ving been demonstrated for reptiles and mammais, it was but natural, as a first step to augment our know\edge of the occurrence of th is structure, to try to find it also in the remaining c1ass of amniotes, viz., birds.

I started this search by the aid of a set of series of the sparrow (Passer

1) See for titles of papers already cited in thc previous communication. the list of literatur~ given there.

2) This is not quite correct. As set forth in the historical survey at the end of the paper, RENDAHL (1924) already before H URER and CROSBY (1926) described this nucIpu5 in Varanus salvator and Alligator mississippiensis, calling it nucleus fasciculi septi.

1094

domestieus), viz., a transverse and a sagittal WEIGERT-PAL~paracarmine series, a horizontal WEIGERT-PAL~alum~carmine series, and a transverse series stained for cells by HUBER's toluidin blue method. Having found the nucleus sought for, it was also studied in a transverse WEIGERT-PAL series, counterstained with various sorts of carmine, of the dove (Columba domestica) and in a transverse HUBER series of the same anima!. This bird, due to the stronger development of the olfactory system, proved better suited for the study of the connections.

An inspection, in the sparrow, of the foremost part of the thalamus, the region where the nucleus of BELLONCI is found in reptiles and mammais, immediately revealed the presence of a clearly circumscribed nucleus, whieh by its general appearance made the impression to be the sought for structure. As in the cases, so far known, it was a small ellipsoidal body, whose neuropil stained strongly with paracarmine. In the dove about the same relations were found. As was to be expected, this clearly circum~ scribed and rather conspicuous nucleus had been described before. It appeared to be the nucleus lateralis anterior of EDINGER and WALLENBERG (1899), a cell group about whieh, despite its distinctness, a great con fusion has arisen, whieh I shall try to disentangle at the end of the paper.

I shall start to put forward my findings in the sparrow, and already now shall speak of a nucleus of BELLONCI, leaving the argumentation for later.

In the sparrow the nucleus of BELLONCI is an ellipsoidal body of dense neuropil with numerous, mostly small cells in it, lying immediately dorsal to the margin of the foremost part of the chiasma, separated, however, from it by the tractus isthmo~optieus (figs. I, 2, 3, 4). The major axis of th is ellipsoidal body extends in a transverse plane from ventromedial to dorsolateraI. and is but little longer than the longer of the minor axes, whieh is directed sagittally. The third axis is considerably shorter than the other two.

The nucleus of BELLONCI lies dorsolateral to the voluminous cell group, mostly designated without specifieation as lateral genieulate, but whieh I agree with KUHLENBECK (1937) in regarding as the ventral lateral geniculate (figs. I, 3). This nucleus beg ins a little more caudally than the nucleus of BELLONCI. Just in front of the latter the nucleus supraopticus and nucleus of the diagonal band of BROCA are situated, the former ventrally and applied to the optie tract, the latter more dorsally (fig. 4). The nucleus of BELLONCI is immediately succeeded by the nucleus rotundus (figs. 3, 4).

The ramus dorsalis of the tractus septo~mesencephalieus courses dorsal to the nucleus of BELLONCI, so that it is wedged in between this tract and the tr. isthmo~optieus (figs. I, 2, 3, 4) . Though closely applied to these tracts, so that it may synapse with them, there is no conclusive evidence, in our WEIGERT-PAL preparations, of such a supply, no more than by the optie tract. As far, however, as it is possible to judge from WEIGERT­PAL preparations, the chief supply of the nucleus of BELLONCI is provided

tr. sept~mesel1e

ventr. I at .,.........~"""'-':..:...""".'. : ..

Idl"Yl. hyper5lr:-~. , i'< tlucl . sept~hipp.--,'......".~,..-;...;.---",-*

Jam. med.

tr. cori-; hab. lat. ant.

-fr. front,a r! neostr. p. m h. sept~ mes en

rdm . dor.s. rec. , pra

dec. supraopt . • V. p.v.

. p.me

tr. sept~\T\eHn ram . dors .

ret. prdeopt .

dec supraopt dors v.p.'/.

1095

l'Iud. interC.lam . 5upr. ", 11 11 11 Sup-

hyperstr. dors.

h~perstr. ventr.p.d . ,. fI ' I v.

dm. hypersi:r.

he 0 str. interm.

~~~~~+'~:-'7,\",c<m.med. dors.

#-<.....,,'-'-'-~..,..,...-::P- p/1laeostr. augm. prlm.

,~~--.,.,r--_ Iam . med. ventr . ...... .. , '"-''-- neostr. front.

8~;.L-- h . {roMeh. e. "eostr. ucl. bas .

tr. str.,.tegm. ~ eer. + quint~frant. nuel. Bellone;

tr. isthrn.-opt. tr. off~dohl1b . lat. chiasma

Fig . 1.

/lUc!. interc. lam . supr. 1/ sup.

hyperstr. dors.

hyperstr. ve ~tr. r. d. 11 11 I/ " .

lam. h'lperst.r.

#8%S7~rlllrn. med. dors.

~~~c.;....:':S.,;.,j--Pl1loeost.r.d'1m. I, ~r.

etio,l,. c-:;,,-,-,",~71"'- lam. me d. ventr. ·

neosh front .

~~~~~~:=:tti7~tr. fr~àr{hJ· neostr. nucl . bas .

h . str,teg-m. ~ eer. + '1uint7fyont. nuc/. Bellorlc;

tr. jsthm~ol>t. nuc\. gen. lat ve"tr.

ir. olfac+hob. löt.

Fig . 2.

Figs. 1 and 2. SPARROW. Cross-sections through foremost part and middle

of nucleus of B EL LONCI, resp., the farmer just in front of the v entra l la teral

genieula te, the la tter a Iittle af ter beginning of this nucleus . WEIGERT- P AL-

paracarmine. X 10.

1096

t r. thdl,front. med 1/ intenn

pala,:ostr.d

tr. str.-teqm.,,~.:.:.....;.~~ +quint:fr.

h: sept:mesenc. .. . rarn. dors . -0.' .:......'-'-~

nuel. Bellonci

h. opt.

nud . ~en . lat. ventr. I. 11 dors. nud. pos~v

td.ect-th . ~ th~tect. "ud. rot.

nucU.r. hab'-ped.

ud. spirif. r·me". i5thrn~opt.

f.mes.l.d .c.

nuc.\. mes. lat . p.v. nuc/. isthmi prine. pal·voc.

h ... tec.t7 spirit. med.

nllef. spi rif. r./at .

Fig. 3. SPARROW. Sagittal section through middle (in transverse direction) of nucleus of BELLONCI. WEIGE/?T-PAL-paracarmine. X 10.

III1t1Jasc.diaf Broe"

dec. . supra ort. dors.

tr. septolnes. MIJl.d.

t r. str~tes'IT1.~cer. +quint,fr.

+sept,mes.r.b.c.

t,.. tha/, Fr. inier ..

!r. nlld. ovoid

tI'. sept7mesenc.

tr.fr"arch . I! ne o:,tr.

uel. pas. palaeostr. augm . tr. fr,arch. 6neostr. p.metl.

+ co rt7hi\b./öt.dnt:.

nuc.1. Bellon,i

h . 0Ft. marS'.

gris. ted. teet .opt.

'-";,~.:..,..:,,~_ hur!. spirif lat.

·:';::';T~+~~nud. mes. \.d.s . .. " c,

nuc.l.poshl ong.med. tr.tC~ct,' bUIID:d IJ I'

Fig. 4. SPARROW. Horizontal section through middle (in vertical direction) of nucleus of BELLONCI. WEIGERT- PAL-alum-carmine. X 10.

EXPLANATION OF SOME OF THE ABBREVIATIONS US ED IN THE FIGURES.

a, differentiated portion of hyperstriatum accessorium (see HUBER and CROSBY, 1929) .

comp. sept.-mes. stro m., component from tractus septo-mesencephalicus to stria medullaris.

gris. tect., griseum tecti, tectal gray of HUBER and CROSBY (1929) .

nucl . ace. post., nucleus accumbens pars posterior.

nucl. bas., nucleus basalis. nucl. intere. lam. sup., nucleus intercalatus

laminae supenons (see KAPPERS, HUBER and CROSBY, 1936).

nucl. intere. lam. supr., nucleus intercalatus laminae supremae (see KAPPERS, HUBER and CROSBY, 1936).

1097

nucl. mes. I. d. c. , nucleus mesencephalicus nucl. post.-interm., nucleus postero-lateralis pars dorsalis centralis. intermedius.

nucl. mes. I. d. s., nucleus mesencephalicus nucl. post.-ventr., nucleus postero-ventralis. lateralis pars dorsalis superficialis. nucl. sept.-hipp., nucleus septo-hippocam-

nucl. periv. m. acc., nucleus periventricularis palis. magnocellularis accessorius (see KUROT- tr. gen.-front. ventr., tractus geniculo-su, 1935). frontalis ventralis (see FREY, 1937).

nucl. periv. m. pr., nucleus periventricularis tr. sept.-mes. r. b. C., tractus septo-mesen-magnocellularis principalis (see KUROT- cephalicus ramus basalis caudalis. su, 1935).

by a ma ss of loosely arranged fine myelinated fibres th at seem to come Erom the dorsal supraoptic decussation (figs. I , 2). These fibres diverge in the direction of the nucleus, embrace and traverse it, but at its lateral side again collect. Farther they could not be followed with certainty in the sparrow. In the dove, wh ere they are much bet ter studied, we shall revert to them.

Also in this bird the nucleus of BELLONCI is an ellipsoid (figs. 5, 6) , but here the major axis , in contradistinction with the sparrow, where it lies in a transverse plane, is directed sagittally, while the longer of the minor axes, which IS but little shorter than the major axis, extends almost vertically.

In the dove the nucleus of BELLONCI shows about the same relationships to the neighbouring nuclei as in the sparrow, but those to the neighbouring and possibly synapsing tracts are somewhat different, in that the ramus dorsalis of the tractus septo-mesencephalicus is only in contact with the oral extremity of the nucleus. Very soon this tract, leaving the nucleus , turns dorsomedially, and runs caudalward along the surface of the brain (figs. 5, 6) .

No more than in the sparrow the origin of the fibres coming from ventromedial could be ascertained in the dove, though they are far more numerous here. All that I can say is that they seem to come from the dorsal supraoptic decussation. Part of them swing medially across the dorsal peduncle of the lateral forebrain bundIe and join the stria medullaris, another part do so with the ramus dorsalis of the tractus septo-mesencepha­

licus. The latter, however, is connected by a compact strand of fibres , coursing along the surface of the brain, with the stria medullaris (fig. 6) . These connecting fibres, in part at least , may be the same as that portion

of the fibres coming from ventromedial which joined the tractus septo­

mesencephalicus. Evidently the loose fibre mass coming from ventromedial represents the

tractus olfacto-habenularis lateralis, which originates in the preoptic and hypothalamic regions. This fibre ma ss has not been seen by HUBER and CROSBY (1929) , who state that they could not identify a tractus olfacto­

habenularis lateralis in birds. The strand of fibres, however, connecting the septo-mesencephalic tract with the stria medullaris, has been observed

Proc. Ned. Akad. v . Wetenseh., Amsterdam, Vol. XLIII , 1940. 71

-lr. sept"mesenc.. vehtr.ldt.

sept .

ir. i nte'rst'~h'fD01;1t:'

tlucl.periv. 1Tl . pr: " 4 11 eet'.

fr. stde[rn. ~ ce" +qvinv.front.

+setlt:-mes.r.b.C. ir. i "fun

nvd. periv. m. p " ~ /1 4CC .

vel1tr. ht! .

" I/ 11

1098

nud. sept-:-hipp. corn. pallii

lam . med. dors. tr. archish .. hab6pr4etorn. h. cort-:hab.lat. nnt. ntos\:r.

palaeosh augrn. /I prlm.

~ii1ii~~~?::" tr: oc.t-:n!esene. ~~~~,;:.-;..;!,- tr. sel"V:lt'\u.ram.ci.

nuel. ,"terst. st.r. term.

nut!. 8elio"c.i i~thrn~ol't.

hlenc.lat. p.dors.

"uel. ge.n.lat. vent.,..

. olf7hab. lai:.

nucl. dec.. 5uprdoptdor.s.

ve"h. te,.4:.

Fig. 5.

neostr.

',tiiP+':"7"ë'-' raid e 0 st r. au gm. 11 .prll,".

co 1'>11". se~t7Il1e5. sir."'.

"""" ~>..-tr: OCC;-01es.

,=,:.;.".;;".,. ,!;i!ol!.. ~';;- tr. i.,ter5t-: hypothaI. tr. sept:-me.s. ram. d.

isth.,.,,,opt.

raSt . telet1dat.p_ dors.

MUel. g-en.lat. vent!: r. olfohab.\ ... t.

nvd. dec. 5upraopt. dors.

Fig. 6.

Figs. 5 and 6. DOVE. Cross-sections through hindmost part of nucleus of BELLONCI and beginning of stria medulla ris, fig . 6 some sections behind fig . 5.

WEîOERT-PAL-paracarmine. X 8.

1099

by H UBER and CROSBY (their component from septo-mesencephalic system to habenula).

The tractus oHacto-habenularis lateralis is not reported here for thc first time for birds, it was described in them long ago as tractus strio­habenularis by MÜNzER and WIENER (1898) and EDINGER and W ALLEN­BERG (1899). Also KAPPERS and THEUNISSEN (1908) mention th is bundIe.

Medial to the nucleus of BELLONCI and coextensive with its caudal haH lies a cell mass, which is closely applied to the dorsal peduncle of the lateral forebrain bundIe (figs. 5, 6). At its beg inning it only covers the lateral aspect of the lateral forebrain bundIe, but gradually it expands medially so as to cover this bundIe dorsolaterally too. Also in the sparrow this nucleus is present, but here it lies farther backward (fig. 7). No doubt this is the crusta peripeduncularis of EDrNGER and W .ALLENI3ERG (1899), which cell mass is only referred to of later authors by GROERBELS (1924), who in the dove and chick is inclined to identify it with his geniculatum laterale tertium anterius 1) and by RENDAHL (1924, p. 315), who could not find it in the chick. It may be the same as the bed nucleus of the tractus thalamo-frontalis medialis of HUBER and CROSBY (1929, p. 89). I suppose this cell group to be the interstitial nucleus of the stria terminalis 2), on the ground that it occupies exactly the same position relative to the lateral forebrain bundIe and nucleus of BELLONCI as the latter does in crocodilians (compare figs. 5 and 6 of the dove with fig. 2d. of Crocodilus porosus in the previous paper).

We shall now put forward our arguments for regarding the nucleus lateralis anterior of birds as the homologue of the nucleus of BELLONCI of amphibians, reptiles, and mammals.

In the first place the position of the two nuclei is quite similar, both being situated in the foremost part of the thalamus, dorsal to the oral extremity of the ventral lateral geniculate, with the restriction, however, that in anures the nucleus of BELLONCI has shifted rather caudad along the dorsal side of the lateral geniculate (AODENS, 1938, fig. 1). In mammals the nucleus of BELLONCI occupies its usu al rostral position, hut here the lateral genicuJate has shifted caudad, so that there is a gap between these nuclei.

As to the development of the nuclei, we are comparing, the nucleus of BELLONCI is known to arise from the ventral thalamus (see ADDENS, 1938). About the development of the nucleus lateralis anterior of birds RENDAHL (1924) and KUHLENHECJ( (1937) unfortunately are at variance. According to RENDAHL (1924), in the chick this nucleus splits oH from the foremost

1) This is not correct. Both in the dove and chick the crusta peripeduncularis lies farther forward and more medially than GROEBBELS' geniculatum laterale tertium anterius. In my opinion the latter is the foremost dorsal part of the tectal gray of HUB'ER and CROSBY (1929).

2) In the previous paper, following CAIRNEY (1926) for Sphenodon, I labelled th is nucleus as the interstitial nucleus of the tractus amygdalo-praeopticus.

71*

1100

upper part of a cell plate, which for the rest gives rise to the ventral lateral geniculate 1) , and thus would belong to the ventral thalamus. According to KUHLENBECK (1937), working also with the chick, the nucleus lateralis anterior, however, is a rostral differentiation of the primordium of the dorsal lateral genieulate, which belongs to the dorsaI' thalamus.

In amphibians as well as in reptiles and mamma Is the nucleus of BELLONCI is an ellipsoid, whose major axis surpasses the langer of the minor axes two times or more in length. In the first class the major axis of the ellipsoid is directed sagittaIly, whereas in reptiles and mammals it is situated in a transverse plane. In the previous paper I explained th is difference by a turning of the nucleus through 90°. It may as well be, however, that it has been brought about by a compression in sagittal direction. Like the nucleus of BELLONCI also the nucleus lateralis anterior is an ellipsoid, with, however, but a slight difference in length between the major axis and the langer of the minor axes.

As to the histologieal structure of the nucleus of BELLONCI, in amphibians this nucleus is a dense ma ss of neuropil, with but a few cells within it, almost all of these being ~ituated outside the neuropil, viz., on its medial side. In reptiles and mammaIs, however, the cells lie within the neuropiI. The avian nucleus lateralis anterior is likewise a dense ma ss of neuropil. with the cells within it.

A comparison of the connections of the two nuclei also strongly speaks in favour of their homology. In the previous paper it was set forth that the chief supply to the nucleus of BELLONCI (in amphibians and crocodilians at least) was by the tractus olfacto~habenularis Jateralis 2) , and that a contribution from the optie might be deemed certain in amphibians, prdbable in reptiles, and not excluded in mam mals. The connection with the optic was confirmed of late by STRÖER (I 939) , who found that in specimens of Triturus taeniatus wh ere in early stages the primordium of one eye was extirpated, the neuropil of BELLONCI on the heterolateral side was smaller than on the other.

As to the connections of the nucleus lateralis anterior, when describing this nucleus in the sparrow and dove, lalready expressed as my opinion

1) As set forth below. the nucleus lateralis anterior is identical with RENDAHL's nucleus fasciculi septi (labelled ä by him). while- the ventral lateral geniculate of KUHLENBECK and us corresponds with RFNDAHL's corpus geniculatum thalamicum.

2) In the previous paper I distinguished in crocodilians a tractus olfacto-habenularis lateralis anterior and posterior. identifying the former with the tractus olfacto-habenularis lateralis of Miss CROSBY (1917) and the latter with her tractus olfacto-habenulari~

posterior. As I now perceive. the latter identification is not correct. The tractus oHacto­habenularis posterior of Miss CROSBY arises near the posterior end of the hemisphere from the nucleus of the lateral olfactory tract and the ventro-medial nucleus. The fibres. however. described by me as tractus dJfacto-habenularis lateralis posterior. from an unknown souree ascend through the forebrain bundIe to the ~tria medullaris. They have already been seen by UNGER (1911) (his tractus transversalis taeniae) in crocodilians and by CAIRNEY (1926) in Sphenodon. Thus the two terms proposed by me have to be dropped.

1101

that its chief supply is by fibres coming from ventromedial and ascending to the stria medullaris, which I interpreted as the tractus olfacto-habenularis lateralis. I could not decide, however, in my WEIGERT-PAL preparations wh ether the optie tract, the tractus isthmo-optieus and the ramus dorsalis of the tractus septo-mesencephalicus, all of which are closely applied to the nucleus lateralis anterior, actually synapse with it. Regarding this, however, the Japanese SHIINA (1932), in his monograph on the nucleus lateralis anterior, gives some, though not very convincing, information. Partlyon the basis of normal preparations (WEI GERT-PAL), partly of MARCHI and G UDDEN experiments, he came to the conclusion that fibres of the ramus dorsalis of the tractus septo-mesencephalicus pass only through the nucleus, but that op tic fibres actually end here.

Contrary to HUBER and CROSBY (1929), who did not see the tractus olfacto-habenularis lateralis, SIiIlNA described these fibres in all the birds, investigated by him, but regarded them as arising in the nucleus lateralis anterior and running in medial direction, partly to join the supraoptie decussations. Doubtless, however, the fibres in question ascend to the stria medullaris, as described and figured here for the dove (figs. 5, 6) .

Finally it may be mentioned that the only connection HUBER and CROSfW (1929) name for the nucleus lateralis anterior is their tractus thalamo­frontalis intermedia lis (better intermedius) . S~IIINA confirms this both in norm al and MARCHI preparations and, moreover, on the same basis, mentions a connection with the tractus thalamo-frontalis lateralis. In my WEIGERT-PAL preparations I can confirm neither of these statements.

From this discussion of the connections of the nucleus lateralis anterior of birds thus much seems to be su re that the tractus olfacto-habenularis lateralis provides the chief supply, and that a connection with the optie is very probable, just the same conclusions we arrived at for the nucleus of BELLONCI of amphibians and reptiles. Thus, with the possible ex cept ion of embryologieal development, all criteria for the homology of nuclei available: position in the adult, connections, histologieal structure, and shape are in favour of the homology advocated by us .

The only other interpretation so far offered of the nucleus lateralis anterior of birds, is by KUHLENI3ECK (1937). As mentioned above, according to him , in the chiek this nucleus is a rostral differentiation of the same cell plate whieh for the rest gives ri se to the dorsal lateral genieulate. H, moreover, it could be proved that the nucleus lateralis anterior receives optie fibres, this nucleus should simply be called pars rostralis corporis genieulati dorsalis. The anterior part of the optie tract, however, whieh, according to KUHLENBECK, possibly supplies the nucleus lateralis anterior in all probability is nothing but our tractus olfacto-habenularis lateralis.

While, apart from KUHLENRECK'S, no attempts have been made to find

homologues for the nucleus lateralis anterior of birds, either lowel' or higher in the scale of vertebrates , it has been tried several times to

homologize the nucleus of BELl.ONCI of amphibians or ovalis of reptiles

1102

with centres of higher forms in a different manner from ours. If these attempts had been successfuI. they would. of course, invalidate one or more of the conclusions arrived at by us, and so we have to discuss them. Por want of spa ce, however, we can do so only with the two most important among these hypotheses, viz., those of HUBER and CROSBY (1929). which is the same as that of KAPPERS (1938), and of LE GROS CLARK (1932).

HUBER and CROSBY (1929) are inclined to homologize their avian nucleus superficialis parvocellularis with the nucleus ovalis of reptiles. This nucleus superficialis parvocellularis is the same as the nucleus of the septo~mesencephalic tract of EDINGER and WALLENBERG (1899). The name was first used by RENDAHL (1924), who, however, under this term included the nucleus lateralis of EDINGER and WALLENBERG. The nucleus superficialis parvocellularis is a band of gray matter along the lateral aspect of the dorsal thalamus throughout almost the whole of its extent, in which the ramus dorsalis of the septo~mesencephalic tract on its way to the midbrain splits up for a great part (fig. 7).

tr. qv i 111.~fto"t. +sept, mu.r.b.c.

nvtl.l'htop.inf.

h. infv .. d.

Fig. 7.

nuc/. il1tet"st. stro te"m. lam. hyp.rs-l:r.

1I med. dors .

neosfr: il1term. + c4 ud.p.3I1t.

l1eostr. cdud.p.post.

hype.str. ventr. p.d. nvel. dorso!at.

ant.p.lat.

l1ucl. tr. sepbnes.

"'S~+?~~.,,:-'-+-_tr. septoll14S. '" ram. dors.

gri5. het . "vel. g-en . lat. dors.

SPARROW. Cross-section approximately through middle of thalamw:. WEIGERT-PAL-paracarmine. X 10.

The first argument of HUBER and CROSBY in homologizing the nucleus superficialis parvocellularis of birds with the nucleus ovalis of reptiles is that the position of the two (dorsal to the lateral forebrain bundie and lateral to the nucleus dorsolateralis anterior) is approximately the same. Prom our side, however, it may be stated that the position of the nucleus

1103

lateralis anterior relative to th is bundIe and nucleus. in the dove (figs. 5. 6) at least. is not so very mueh different.

The seeond argument of HURER and CROSBY in favour of the homology of the nucleus superficialis parvoeellularis and nucleus ovalis' is derived from the eonneetions. Further study of their allig2tor material suggested that there are fibres from the media I forebrain bundIe (or assoeiated with it) which swing around the ventral side of the lateral forebrain bundIe and into the nucleus ovalis. Sueh fibres would be homologous with the ramus dorsalis of the septo-meseneephalic traet and the nucleus with the nucleus of that traet or nucleus superficialis parvoeellularis. In the text-book of KAPPERS. HUBER and CROSBY (1936) this statement. however. is not repeated.

Contributory evidenee to a homology of the nucleus superficialis pa rvo­eellularis and nucleus ovalis. aeeording to HUBER and CROSBY. is found in the distribution of optie fibres to both these nuclei. For the nucleus ovalis. as set forth above. the presenee of optie connections may hold good. but neither for the sparrow. nor the dove I ean eonfirm HUBER and CROSBY's findings of optie fibres going to the nucleus superficialis pa rvo­eellularis.

Our ehief objection against the homology advoeated by HUBER and CROSBY. is that a connection of the nucleus superficialis parvoeellularis with the tractus olfaeto-habenularis lateralis is entirely lacking. Moreover. and this also is an important point. th is nucleus is voluminous and of eonsiderable length. extending from about the beginning of the thalamus to the posterior commissure. whereas the nucleus ovalis is small and eonfined to the foremost part of the thalamus. And. as the latter is ehiefly an olfaetory centre. it is extremely improbable that in the mierosmatie birds it has developed into a strueture several times its size.

The seeond attempt. in which we are concerned. at homologizing eertain thalamic centres is LE GROS CLARK's (1932) regarding the nucleus of BELLONCI of amphibians as the forerunner of the dorsal lateral genieulate of mammals. Already in reptiles. aeeording to LE GROS CLARK. a dorsal lateral genieulate may be reeognized (the homologue eonsequently. in his opinion. of the nucleus of BELLONCI of amphibians). In the American alligator. aeeording to LE GROS CLARK. this centre is represented by a differentiated lateral portion of the nucleus dorsolateralis anterior. described by HUBER and CROSBY (1926). which is said by these authors to reeeive some optie fibres . In Sphenodon these superficial eells even form a fairly cireumseribed nucleus. whieh has been termed the dorsal nucleus of the lateral geniculate body by CAIRNEY (1926) and DURWARD (1930).

Thus LE GROS CLARK's view about the fate of the nucleus of BELLONCI of amphibians in amniotes (represented diagrammatieally in fig. 3 of his paper. 1932) is entirely different from ours.

It must be ohjeeted to LE GROS CLARK that it is very doubtful if the differentiated lateral portion of the nucleus dorsolateralis anterior of the

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American alligator, leaving alone if it is a constant feature, really receives op tic fibres. In the transverse WEIGERT-PAL~paracarmine series of this animal at my disposal the staining of the ce lis was not sufficient to decide whether this differentiated portion was present, but I greatly doubt if op tic fibres end in the reg ion where it must be situatcd. Moreover, this cell group, if present at all, does not correspond with the dorsal lateral geniculate, described by CAIRNEY (1926) and DURWARD (1930) in Sphenodon. The latter, in my opinion, really is the homologue of the mammalian dorsal lateral geniculate. But also in the crocodilians there are a ventral and a dorsal lateral geniculate, the corpus geniculatum laterale of the alligator of HUBER and CROSBY, according to my interpretation, being the dorsallateral geniculate, while their nucleus tractus tecto~thalamici cru cia ti is the ventral one (see fig. 3 of the previous paper).

As stated at the outset, despite its distinctness, a great confusion prevails about the avian nucleus I interpret as the nucleus of BELLONCI. In order to try to make an end to this con fusion a short historical survey about the nuclei involved in it, may be appended here.

The first authors to notice our nucleus were EDINGER und WALLEN BERG (1899) in their classica I paper on the bird's brain, who, however, do not mention it in the text, but only indicate it in their figures.

KAPPERS (1921) in the first edition of his text~book in two figures . relating to Pratincola rubicola (Vol. 11, figs. 468, 469; p. 875, 876) labelled a nucleus in the dorsolateral part of the thalamus as nucleus lateralis anterior. It appears, however, from the text that the nucleus lateralis of EDINGER and WALLEN BERG is meant.

Not before the lapse of the quarter of a century af ter EDfNGER and WALLENBERO's (1899) paper, the nucleus lateralis anterior was seen again, by RENDAHL (1924), in the embryo and adult chick. He, however, erroneously identified it with the nucleus of the septo~mesencephalic tra ct

of EDINGER and W ALLENRERG, calling it nucleus fasciculi septi, and thus gave rise to the subsequent confusion. To the nucleus of the septo~

mesencephalic tract RENDAHL gave a new name. viz., nucleus superficialis parvocellularis, including with this cell group the nucleus lateralis of EDINGER and WALLENBERG. RENDAHL found his nucleus fasciculi septi also in reptiles (Varanus salvator and Alligator mississippiensis). From his description it is clear that this is no other than the nucleus of BELLONCI (alias ovalis) of these animals. Thus RENDAHL (1924) already before HUBER and CROSBY (1926) observed the nucleus ovalis, and moreover, already recognized its homology with the nucleus lateralis anterior of birds.

CRAIGIE (1928) has followed RENDAHL in his error, the nucleus he describes in humming birds as nucleus tractus septi, being the nucleus lateralis anterior of EDINGER and WALLENBERG.

It was HUBER and CROSBY (1929), who in their comprehensive studies on the avian diencephalon for the first time correctly identified the nucleus

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lateralis anterior. They failed, however, to see that this nucleus was mistaken by RENOAHL for the nucleus of the septo-mesencephalic tra ct.

In his second paper on the avian brain (kiwi) CRAIGIE (1930) still designates the nucleus lateralis anterior as nucleus tractus septi. Moreover, he now described another cell group immediately dorsomedial to the latter as nucleus lateralis anterior, whereby the prevailing confusion was still enhanced. In his last paper, dealing with this subject, CRAIGlE (I 931), however, realized that his nucleus tractus septi was identical with the nucleus lateralis anterior of EDINGER and WALLEN BERG , and that, con se­quently, the nucleus of the kiwi, Iying dorsomedial to the latter and called nucleus lateralis anterior by him, was something else. In my opinion this nucleus is the crusta peripeduncularis of EOINGER and WALLEN BERG, our interstitial nucleus of the stria terminalis (figs. 5, 6, 7).

Finally it may be mentioned, that, like H URER and CROSBY, to whom belongs the credit to have done so for the first time, also SHllNA (1932) and K UHLENBECK (1937) correctly identified the nucleus lateralis anterior.

SUMMARY.

It is argued that the nucleus lateralis anterior of birds, first described by EOINGER and W ALLE[\;BERG (1899), is the homologue of the nucleus of BELLONCI of amphibians, reptiles and mammals.

The crusta peripeduncularis of EOINGER and W AI.LENBERG is homologiz­ed with the interstitial nucleus of the stria medullaris.

L I TER A TU R E .

AOOENS , J. L., The presence of a nucleus of BELI.ONCI in reptiles and mamma Is . Proe. Kon. N ed. Akad . v . Wetensch. , Amsterdam. 11 ; 1134- 1145 (1938) .

CRAIGI E, E . H ., Observations on the brain of the humming bird (Chrysolampis mosquitus Linn. and Chlorostilbon caribaeus Laur.) . J. Comp. Neur. , 45, 377-~81

(1928) . - - ---, Studies on the brain of the kiwi (Apteryx australis). Ibid .. 49. 223- 357

(1930) . The cell masses in the dil'ncephalon of the humming bird. Proc. Kon. Akad . v . W etensch., Amsterdam. 34, \038- 1050 (1931) .

EDINGER, L. und WALLENBEIW, A .. Untersuchungen über das Gehirn der Taubpn. Anat. Anz. , 15, 245- 271 (1899).

FREY, E ., Vergleichend-ana tomische Untersuchungen über die basale optische Wurzel u.s.w . Schweiz. Arch . Neur. u. Psychiatr., 39, 255-290; 40, 69- 126 (1937) . Also D iss. Zürich 1937. Zürich, Art. Inst. ORELL F ÜSSLI.

GROEBBELS, F .. Untersuchungen liber den Thala mus und das Mittelhirn der Vögel. Anat. Anz., 57, 385- 415 (1924).

HUBER, G. C. and CROSBY. E . c., The nuclei and fiber paths of the av ian diencephalon, with consideration of telencephalic and certain mesencephalic centers and

connections. J. Comp. N eur., 48. 1- 225 (1929) . KAPPERS, C. U . ARIËNS, Die \"l'rgleichende Anatomie des Nervensystems der Wirbeltierr

und des Menschpn . 11. Haarlem, De Erven F . BOHN (1921) .

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KAPPERS, C. U. ARIËNS, HUBER, G. C. and CROSBY, E. C., Tbe comparative anatomy of the nervous system of vertebrates, including man. 2 Vois. New-Y ork, Tbe MACMILLAN Company (1936).

----- und THEUNISSEN, W. F ., Die Phylogenese des Rhinencephalons, des Corpus striatum und der Vorderhirnkommissuren. Fol. Neur-biol., 1. 173-288 (1908).

KUHLENBECK, H ., The ontogenetic development of the diencephalic centers in a bird's brain (chick) and comparison with the reptilian and mammalian dien ce­phalon. J. Comp. Neur., 66, 23-75 (1937).

KUROTSU, T., Ueber den Nucleus magnocellularis periventricularis hei Reptilien und Vögeln. Proc. Kon. Akad. v. Wetenseh., Amsterdam, 38, 784-797 (1935) .

MÜNZER, E . und WIENER, H., Beiträge zur Anatomie und Physiologie des Centralnerven­systems der Taube. Monatsschr. Psychiatr. u. Neur. , 3, 379-406 (1898) .

RENDAHL, H ., Embryologische und morphologische Studien über das Zwischenhirn beim Huhn. Act. Zool., 5, 241-344 (1924) .

SHIINA, J.. Der Nucleus lateralis anterior der Vögel mit Berücksichtigung der primären Endung des Nervus opticus. Jap. J. Mcd. Sc. I. Anat., 3, 67-141 (1932).

STRÖER, W. F. H ., Zur vergleichenden Anatomie des primären optischen System bei Wirbeltieren. Z. Anat. u. Entw. Gesch., 110. 301-321 (1939) .

UNGER, L., Untersuchungen übcr die Morphologie und Faserung des Reptiliengehirns. 11. Das Vorderhirn des Alligators. Sitz. Ber. Akad. Wien, Math.-Naturw. KI., 120, Abt. 3, 177-202 (1911).